It has been known to grow algal biomass cultures in open air and closed pond systems. Open air cultivation of an algal biomass has many problems, one of which is the possibility of contamination of the algal growth by constituents in the air that contact the growing culture. Representative open air systems for cultivation of algae are shown in U.S. Pat. No. 3,650,068; U.S. Pat. No. 3,468,057; U.S. Pat. No. 4,217,728.
In order to properly grow algal cultures in a closed system several conditions must be present. There must be constant agitation of the aquaculture medium (liquid suspension) containing the growing algae, heating for maintenance of a proper climate within the closed systems, exposure of the algae to photosynthesizing light, and an adequate means to replace carbon dioxide (CO.sub.2) to the aquaculture medium due to losses during photosynthesis. The absence of these conditions could prove fatal to the growing cycle of the algae.
As stated, closed systems for growing algal cultures are known, however, unlike open systems, one of the main problems in these systems is the efficient replacement of the CO.sub.2 to the aquaculture medium for consumption during photosynthesis in the algal biomass during growth. The closed system, unlike the open air system cannot absorb CO.sub.2 from the open atmosphere. So, there must be an artificial means by which CO.sub.2 can be resupplied to the medium and atmosphere within the closed system.
Prior art closed systems all have methods by which CO.sub.2 is replenished by the system. Generally the CO.sub.2 is replenished by bubbling it into and through the medium. The prior art closed systems that use a bubble method for replacing CO.sub.2 are represented U.S. Pat. No. 3,955,317; and U.S. Pat. No. 4,253,271.
However, none of the prior art of systems have an effective way to resupply CO.sub.2 to the medium alone and the medium and atmosphere together within the closed system.